Modem stuck in reboot loop, but impossible to reach KPN support

My modem stuck in infinite reboot loop.

When I plug in modem, all lamps (except wi-fi) goes green and everything looks normal, like modem loading and establishing an internet connection.

But then wi-fi lamp goes green for a second or two, then all lamps goes off and after a pause power lamp turns red. It stays red for a couple minutes and then loop above repeats.

I tried to reset modem, but it does not react to reset button at all. I assume it’s because modem is in reset mode constantly.

I tried to turn modem off for a some time and on again - it does not help.

I tried to contact KPN support, but web interface repeat recommending actions I’ve already taken.

I tried to call KPN support by the phone number I found on the forum (not even on KPN site) - but it’s full Dutch. I don’t speak Dutch, so cannot understand it - and voice assistant just hang up call after repeating couple Dutch phrases. 

This post is a desperate attempt to get KPN help. For now it looks easier to switch to a different provider than to get a KPN support.